In the fuel cell field, there is an attempt to improve fuel cell performance by focusing on catalyst layers.
For example, such a catalyst layer is disclosed in Patent Literature 1, that a catalyst is uniformly supported on the surface of a mesoporous carbon support since the average pore diameter of the support agrees with the average particle diameter of a catalyst complex.
Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2015-071784
Patent Literature 2: JP-A No. 2002-025560
Patent Literature 3: International Publication No. WO2007-126153
Patent Literature 4: JP-A No. 2004-311060